Cathode structure



1945- P. G. CHEVIGNY GATHODE STRUCTURE Fil'ed Dec. 8, 1942 IN V EN TOR.

Patented Jan. 23, 1945 CATHODE STRUCTURE.

iaul Georges Chevigny, New York, N. Y., assignor to Federal Telephone and Radio Corporation, Newark, N. J., a corporation of Delaware Application December 8, 1942, Serial No. 468,199

8 Claims.

This invention relates to improvements in cathode structure, and more particularly to a cathode for Vacuum tubes adapted to be heated by bombardment.

An object of this invention is to provide a novel unipotential cathode of high emission.

A further object of this invention is to form a built-up cathode which has a larger emitting surface than similar cathodes heretofore proposed.

A more specific object of this invention is to provide a substantially cylindrical cathode in which the cathode emitting surface is formed by a plurality of circumferentially juxtaposed rods or wires which when heated touch one another so as to form an effectively continuous emitting surface.

Other objects and advantages of the present invention will become apparent from the following description of a preferred form of cathode, together with a modification thereof, illustrated in the accompanying drawing, in which:

Fig. 1 is a vertical longitudinal section of a novel cathode structure formed in accordance with the present invention;

Fig. 2 is a horizontal cross-sectional view taken along the line 22 of Fig. 1; and

Fig. 3 is a partial cross-sectional view showing a modified structural detail.

As is clearl illustrated in Figs. 1 and 2, the cathode emitting surface is formed of a plurality of longitudinally extending parallel rods or wires which may be made of thoriated tungsten or from equivalent material. A sufficient number of the rods ID are circumferentially mounted in end supports i2 and It to form a substantially cylindrical cathode surface surrounding and coaxial with a centrally positioned heater coil it. The rods It are preferably mounted in annular grooves of the end members 12 and M, as by Welding. In order to take care of expansion of the rods in under the heating action of the filament Po, the rods are preferably slightly spaced from one another so that when they expand under this heating action, they will touch one another to form a continuous cathode surface. It is contemplated that the cathode will be of such a type that the rods Ill and will be heated by the filaments It by bombardment, although the invention is not intended to'be limited to this specific form of heating. The filament I 6 is preferably supported by a suitable centrally positioned rod [8 while the cathode as a whole may be supported by a plurality of circumferentially supported rods 20 attached about the periphery of the cylindrical support 12. The ends of the filament, the rod l8 and the rods 2|] will in turn, extend through and be supported by a suitable glass seal for the tube (not shown).

In order to increase the thermionic efficiency .of the cathode and decrease the cooling effect of the supports, heat screens may be provided at one or both ends of the cathode structure. Fig. 1 shows an example of such heat screens at 22, these being attached in any suitable manner to the lower surface of the lower end member [4.

The manner in which the rods [0 may be circumferentially supported may be varied, if desired, for example in the manner illustrated in Fig. 2. In this form of invention the rod H0 are connected about the periphery of an outwardly extending reverse flange I28 on the end of the support I I2. A ring I30 surrounds the ends of the rods 1 l0 and holds them firmly in place against the surface of the flange I28. Again, it is contemplated that initially the rods H0 will be slightly circumferentially spaced, to take care of the increase in diameter of the rods when heated.

An advantage of the structures illustrated in Figs. 1 and 2, lies in the fact that the rods forming the cathode surface being cut in short lengths can readily be carburized in advance before being assembled. Additionally, since in their heated condition the rods will be substantially tangent to one another, the emitting surface of the oathode is increased over a comparable cathode having a smooth cylindrical emitting surface. The diameter of the rods is so chosen that the depth of the space between the two wires is small with respect to the distance between the cathode and grid. Particularly in the case of such tubes when used in pulse transmitters, this distance is of no importance, as the grid voltage will be very high and will easily draw electrons fr0mbetween the two rods.

It is contemplated that various changes and modifications coming within the scope of the present invention may be made by those skilled in this art. In particular, details in the matter of mounting the rods forming the cathode structure can be effected without departing from the scope of this invention as set forth in the objects and the claims which follow.

I claim:

1. A hollow, self-supporting cathode structure comprising a plurality of circumferentially arranged parallel wires, and separate means at opposite ends of said wires for holding them in their circumferentially arranged position.

2. A cathode for vacuum tubes and the like,

comprising, in combination, a plurality of circumferentially arranged parallel wires, means at each end of said wires for holding them in their circumferentially arranged position, and means positioned within the circumferentially arranged wires for heating them by bombardment, the wires being so circumferentially spaced that when heated they will expand sufficiently to touch one another and form a continuous cylindrical cathode about the heating means.

3. A cathode structure comprising, in combination, a cylindrical cathode support, a plurality of wires connected at one end parallelto one another about one end of said support, and a cup-shaped member connected to and about the other ends of said wires.

4. The combination according to claim 3, in

combination with cathode heating meansinside of the circumferentially arranged wires, said wires being connected to the end of the cathode a substantially continuous cylindrical cathode surface. 1

5. A cathode structure comprising in combination, a cylindrical cathode support having one end formed with a longitudinally re-entrant annular notch, a plurality of wires welded at one end in said notch parallel to one another, and a cup-shaped member formed with a narrow annular groove receiving and supporting the other ends of said Wires.

6. The combination according to claim 5 in combination with cathode heating means positioned inside of the circumferentially arranged wires, and heat shields mounted on the bottom of said cup-shaped member.

7. The combination according to claim 5, in combination with cathode heating means inside of the circumferentially arranged wires, said wires being mounted in said annular notch and in said annular groove in such a manner that the wires will be circumferentially spaced when cold, the

spaces being such that the wires will touch when heated to form a substantially continuous cylindrical cathode surface.

8. A cathode structure, comprising in combination, a cylindrical cathode support having one end formed with an outwardly turned reverse flange, a plurality of wires mounted at one end about the periphery of said flange, parallel with one another, a clamping ring fastened about one end of the wires, and means at the other end of the wires for holding them in their circumferentially arranged parallel positions.

PAUL GEORGES CHEVIGNY. 

